My !995 Astro"s heater control hisses when put in the Defrost mode. I have already repalced the control with a new one and no help. Also air will come out the vents but will not devert to the windsheild. It seems as if one of thevacuum lines is clogged up. Is this possible?

Check for a broken; leaky vacuum hose. Otherwise; will the vents switch from floor to dash vents (the ones that blow at your face) when in any other modes; like A/C or heat? If not; then the 'mode door acutator' may be jammed or broke.

I took the cover off the to watch and see if the doors were opening and yes when the engine is cranked the doors will open but put the control back on heat and they don't close. :banghead: :banghead: Help